Parallel optical transceiver modules typically include a plurality of laser diodes for generating optical data signals, laser diode driver circuitry for driving the laser diodes, a controller for controlling operations of the transceiver module, receiver photodiodes for receiving optical data signals, receiver circuitry for demodulating and decoding the received optical data signals, and monitor photodiodes for monitoring the output power levels of the laser diodes. Parallel optical transceiver modules typically also include an optical subassembly having optical elements that direct the optical data signals produced by the laser diodes onto the ends of optical fibers and that direct optical data signals received over optical fibers onto the receiver photodiodes.
The laser diode driver circuitry is typically contained in an integrated circuit (IC) having electrical contacts pads that are electrically coupled by electrical conductors (e.g., bond wires) to electrical contacts pads of the laser diodes. The number of laser diodes that are included in a parallel optical transceiver module depends on the design of the module. A typical parallel optical transceiver module may contain six laser diodes and six receiver photodiodes to provide six transmit channels and six receive channels. A typical parallel optical transceiver module that has no receiver photodiodes (i.e., an optical transmitter module) may have, for example, twelve laser diodes for providing twelve transmit channels. The laser diode driver ICs that are commonly used in these types of parallel optical transceiver or transmitter modules generate large amounts of heat that must be dissipated in order to prevent the laser diodes from being adversely affected by the heat. Due to the large amounts of heat generated, the tasks associated with designing and implementing a suitable heat dissipation system are challenging.
In many parallel optical transceiver or transmitter modules, openings exist in the modules through which airborne dust, dirt, gasses, or other particulates may enter the module. Ingress of such airborne matter into the module can sometimes cause problems in the modules. For example, ingress of dust into a part of the module that contains the laser diodes can potentially block light output from the laser diodes or received by the photodiodes, which, in turn, can lead to performance issues. Some modules have relatively open designs that enable them to be assembled at lower costs and that facilitate the evaporation of moisture in the modules. Therefore, while an open module design provides certain benefits, such designs are susceptible to problems associated with the ingress of dust, dirt, gases and other airborne matter. In addition, some modules are required to pass mixed flow gas (MFG) tests, during which a module is placed in a chamber and exposed to aggressive chemical gases, such as fluorine and chlorine, for example. These gases can find their way into a module and erode metal components of the module (e.g., bond wires, conductors, etc.), thereby causing damage to the module that can lead to performance problems.
A need exists for a parallel optical transceiver module that has protection against ingress of airborne matter such as dust, dirt, gases, and other airborne particulates that can harm the parallel optical transceiver module.